(CBS SF) — Blizzard and avalanche warnings have been issued for much of the Sierra Nevada and Lake Tahoe area.

The National Weather Service said a Winter Storm Warning was in effect until 4 a.m. Friday in the Sierra for areas above 5,500 feet, while a blizzard warning was in effect for elevations above 6,500 feet.

Travel was reported to be very difficult to impossible, with damage to trees and power lines is possible. Snowfall accumulations of two to four feet were likely above 5,500 feet with local accumulations up to six feet over the peaks.

On Interstate 80 near Donner Summit Wednesday, a jackknifed big rig and other crashes had shut down traffic in both directions for about two hours.

Winds gusts as high as 60 mph or higher were causing whiteout conditions and significant drifting of the snow was likely, the weather service said.

Meanwhile, the Sierra Avalanche Center in Truckee issued a Backcountry Avalanche Warning for the greater Lake Tahoe area from Wednesday afternoon through 7 a.m. Friday morning.

The affected area is the Central Sierra Nevada mountains between Yuba Pass (Hwy 49) on the north and Ebbetts Pass (Hwy 4) on the
south, including the greater Lake Tahoe area.

Caltrans on Wednesday closed State Route 88 at the Carson Spur for avalanche control.

The center warned people to expect widespread, large, and destructive avalanche activity in the mountains.